Flash point testing device including cooling means for the flash chamber



w. v. cRoPPr-:R ETAL 3,521,480 FLASH POINT TESTING DEVICE INCLUDINGCOOLING- MEANS July 21, v19.70

FOR THE FLASH CHAMBER 3 Sheets-Sheet l Filed June 14. 1967 Minima/avrJuly 21, 1970 w. v. cRfoPPr-:R ET AL 3,521,430

FLASH POINT TESTING DEVICE INCLUDINGCOLING MEANS FR THE FLASH CHAMBERFiled Junel4. 1967 Y 3 Sheets-Sheet 2 W. v. CROPPER ETAL FLASH POINTTESTING DEVICE INCLUDING COOLING MEANS Julyizl, 1970 FOR THE FLASHCHAMBER 3 Sheets-Sheet 3 Filed June 14, 1967 United States PatentABSTRACT F THE DISCLOSURE An automaticvash' point testing device havinga heating chamber for receiving a continuous liquid vsample stream andincluding an electricallyv powered cartridge ,heaterl for heating thesample. A stainless spiral is mounted on the outside of the cartridgeheater to prov duce turbulence in'the liquid sample.A The liquid samplepasses upwardly'around the cartridge heater and into ia passageway whereit is mixed with' incoming air. The

'resulting mixture is passed upwardly into a flash chamber Where anair-vapor mixture passes upwardly between a pair of sparking electrodes.When the mixture becomes rich enough to .fbe ignited lby the sparks, aflash occurs within the ash chamber, and is detected by a differentialthermocouple arrangement, which produces an `output signal applied to amagnetic amplifier. The magnetic amplifier in turn produces a controlsignal which stops a series of heating mode functions in an automaticcontrol system, and initiates a plurality of cooling mode functions. Thecooling mode functions are continued for a timed cooling period, afterwhich another heating period is automatically started. The heating modefunctions include a continuous increase in power to the cartridge heaterby means of a motor-driven variable transformer, a continuous sparkgenerator controlled by a pulse generator, the energization of a heatingsignal lamp, and the energization of the heating coil for the cartridgeheater. The cooling mode functions include the timing of apreselectedcooling period, the diversion of the continuous liquid sample streamfrom the liquid feed line to the air feed line for rapid cooling of theflash chamber and the thermocouple therein, the production of a negativeD-C signal which drives the temperature recorder downscale to, preventovershoot and clearly indicate the flash point on the temperaturerecord, the actuation of a second motor in the variable transformer toreverse the movement of the sliding contact therein, and energization ofa cooling signal lamp.

f yThe present invention relates generally to automatic vash pointtesting devices and, more particularly, to an improved automatic ashpoint testing device of the type that is capable of receiving acontinuous liquid sample and maintaining a continuous record of thesample temperature and the ash points detected for the sample.

It is a primary object of the present invention to provide an improvedflash point testing device which is capable of automatically determiningthe Hash point of a liquid sample with a high degree `of accuracywithout the necessity of a preliminary estimate of the flash point toVlbe determined. In this connection, another important objective of thisinvention is to provide such a device which is capable of automaticallydetecting ash'points occurring over a wide temperature range without anypreliminary setting for different samples.

Another object of the present invention is to provide an automatic flashpoint testing device of the foregoing type which greatly reduces thepossibility of missing the flash point of any given sample, even wherethe ash point 'ice of the sample is completely unknown 'before itistested. A related object is to prov/ide such a device 'whichfreliablydetermines the flash point of aliquid sample in 'single test, so thatthe test does not have/to4 be repeated for any given sample,therebyrreducing the overalltesting time required for a large number ofsamples.

It is a further object ofthe invention to provide anim proved automaticflash point testingideviceof the type described above which eliminatesor at least'reduces decomposition of the liquid, and the resultantfoulingfl'hus, it is an object to provide such a` device which requireslittle maintenance with attendant reductions in instrument down time,and increased efficiency. y i .y

Still another object of the present invention is to pro'- vide animproved automatic flash point testing device which achieves rapidcooling between successive heating periods without a supplementarycooling system. i

Yet another object of this invention is to provide anantomatic flashpoint testing instrument of thetype described above which includesIimproved limiting or safety features to prevent overheating and toreduce testing time.

A still further object of the invention is to provide such an improvedautomatic ash point testing device which permits different timed coolingperiods to be selected for different samples or groups of samples.

It is another object of this invention to provide an im proved automaticflash point testing device which prevents overshoots on the temperaturerecord so as to provide a clear and accurate record of the detectedflash points.

Other objects and advantages of the invention will become apparent uponreading the following detailed description and upon reference to thedrawings, in which:

FIG. l is a diagrammatic illustration of an automatic flash pointtesting instrument embodying the present invention with the structureforming the flash test chambe being shown in vertical section;

FIG. 2 is an elevation view, partially in section, of an actual ashpoint testing instrument embodying the system illustrated in FIG. l;

FIG. 3 is an enlarged vertical section taken along line 3 3 in fFIG. 2;and

IFIG. 4 is a schematic circuit diagram of the electrical control systemincluded in the instrument of FIGS. 1 through 3.

While the invention will be described in connection with vcertainpreferred embodiments, it will lbefunderstood vthat it is not intendedto limit the invention to these particular embodiments. On the contrary,it is intended to cover'all alternatives, modifications, and equivalentsas may lbe included within the spirit and scope of the invention as de.-Iined by the appended claims. z

Turning now to the drawings and referring first to FIGS. 1 and 3, theliquid sample to be tested is introduced into the instrument through asupply line 10 which includes a pressure regulating valve 11. In Vatypical operation, the liquid sample isfed at a rate of about 50mL/minute and at a temperature at least 30 F. below its flash point.During the heating 'period of each test cycle, the liquid sample flowsthrough a three-way solenoid-operated control valve 12 into the lowerend of a heating chamber 1 3 formed by a cylindrical casing 14. Astainless steel well 15, into which is inserted a cartridge heater 15b,is mounted concentrically within the casing 14 to form an annularchamber through which the liquid sample passes as `it is heated. Astainless steel spiral 15a is fixed to the outer surface of the well toprovide turbulence, prevent char-1'- neling ofthe liquid and to promoteheat transfer. At the top of the heating chamber 13, the liquid sampleexits through a longitudinal passageway 14a formed'in `the upper end ofthe casing 14 for discharging the sample into a flash chamber 16formedby a second casing 1'] it is' mixed with air introduced into thepassageway 14a from `a supply line including a pressure Yregulatingvalve V21. In a typical operation, the air is fed into the sample 1stream between the heater and the vflash chamber at a rate of 1600Ink/minute. The air supplied to the passageway 14a through the supplyline 20 mixes with the liquid sample and passes upwardly through thepassageway 14a 'into theflash chamber 16 and is finally exhausted fromlthe top of the flash chamber through a vapor exhaust line 22; Theliquid portion of the sample entering the ash chamber 16 runs to thebottom of the chamber and is drained out through a liquid` drain line 23connected to `a conventional llame arrester 23a. As the temperature ofvtheV liquid sample is increased, more and more of the sample isconverted to the vapor phase and rises to the top of the ash chamber 16along with the air. Consequently, as the sample heating continues, theair-vapor mixture rising upwardly through the flash chamber 16 becomesricher and richer until it eventually reaches its V:flash point.

In order to test the liquid sample for its flash point, a pair of spacedelectrodes 24 and 25 are provided'within the flash chamber 16 and areconnected to an electrical spark- `ing system which causes repetitivehigh voltage sparking between the two electrodes 24, 25. A typicalsparking frequency, for example, is one spark per second. Thus, as soonas the air-vapor mixture within the flash chamber reaches its flashpoint, a minor explosion occurs within the ash chamber, producing asmall llame slightly below the electrodes 24, 25. The temperature of theliquid sample is continuously sensed and recorded by an automaticcontrol system including a recorder 26, a measurement control unit 27,and a flash point control unit 28, which also control the cyclicheating, cooling, sparking, and other functions which must be repeatedfor each test cycle.

Turning now to the schematic circuit diagram in FIG. 4 for a moredetailed understanding of the automatic lcontrol system in theillustrative instrument, the operator :turns the instrument 0n manuallyby closing a main onlofi? switch 30. As will be apparent from theensuing description, this is the only manual operation required by thisinstrument, except when it is desired to adjust the automatically timedcooling period to be discussed below.

P2 to their normal open positions to remove power from the entirecontrol system. v

As soon as the instrument is turned on, the heating coil HC1 of a spaceheater 32 (FIG. 2) mounted on the in` side wall of the instrumenthousing is energized to warm up the interior of the instrument. Thetemperature maintained within thevinstrument housing by the space heater32 is controlled by a thermostat TS1 connected in series with thel spaceheater coil HC1.

Turning on the instrument also supplies power to the primary winding Tlaof a transformer T1, so that the secondary winding Tlb thereof suppliespower to a magnetic amplifier 33. The purpose of the magnetic amplifier33, which is normally turned off, is to produce a predetermined outputsignal in response to a triggering input signal produced by theoccurrence of a flash, as will be described in more detail below.I'tvhas been found .that

the use of a magnetic amplifier assures reliable detection of the ashes,even over long operating periods. A plurality of diodes D1 through D5are connected to the amplifier coils in the conventional manner torectify the A-C power input from the transformer T1 (D1, D2,` D4, D5),as well as the amplifier output signal (D3).

In accordance with one important aspect of the present invention, theelectric sample heater is operatively associated with an automaticcontrol means which automatically increases the power input to theheater at a controlled rate until the iiash point of the sample isreached, at which time the power to the heater is automatically cut offuntil the next test cycle is initiated. Thus, in the illustrativecontrol system of FIG. .4, closing the on-off switch 30 supplies powerto the cartridge heater coil HC2 connected in series with a motor-drivenvariable transformer 34 which automatically increases the power input tothe coil HC2 until a flash point is detected, or simulated by a limitingor safety feature to be described below. During the heating period atthe beginning of each test cycle, the sliding contact on the coil 35 ofthe transformer is advanced at a constant rate designed to increase thesample temperature at a substantially constant rate, i.e., so that thesample temperature profile is substantially linear.

The automatic advancing movement of the sliding contact on the coil 35is controlled by a heating mode motor M1 which is energized via a seriesarrangement of (1) a normally closed cam-controlled switch CS1, (2) apole P6 of a fast-acting triple pole, double throw relay K3, the pole P6being in its normal position against contact P617, and (3) a normallyclosed pole P7 of a time delay relay TD1. Thus, the heating mode motorM1 is operatively connected across the power lines L1, L2 as long asswitch CS1 and pole P7 remain closed and pole P6 remains in contact withP6b. This mode of operation continues throughout the heating period,continuously increasing the sample temperature until a flash point isdetected or simulated, at which time the sample heating is promptlyterminated and a timed cooling period is initiated by automatic controlmeans to be described below.

The automatically varying power input provided by the improved controlsystem of this invention represents a significant improvement in the artof automatic flash point testing instruments. When the power input tothe sample heater is xed at a preselected value, as in certain prior artdevices, the sample temperature may rise quite rapidly at first, but thetemperature profile gradually fiattens out and tends to approach ahorizontal line as the tiash point is approached. Such systems areperfectly acceptable in applications where the flash point of the samplebeing tested can be accurately estimated in advance, but seriousshortcomings maybe encountered when accurate estimates cannot vbe made.Thus, if the actual ash point of the sample is higher than expected, forexample, the temperature curve may level olf below the true Iflashpoint, with the result that considerable time is wasted before it isdiscovered that the flash point has not been achieved and the test mustbe re-run after making suitable adjustment of the fixed power input tothe heater. Similarly, if the flash point is lower than expected, thetemperature may be rising at such a rapid rate at the true flash pointthat it cannot be detected, and again the test must be repeated at adifferent setting after it is discovered that the flash point has beenmissed.

With the improved control system provided by'this invention, the powerinput to the sample heater is continuously increased at a controlledrate, so that the temperature profile is substantially linear. Thus, thesample temperature increases at a somewhat slower rate, compared Iwiththe prior art systems, at the beginning of the heating period, andcontinues to increase substantially that same rate until the ash pointis reached. Consequently, it is not necessary to estimate the flashpoint, because it can be detected with the same degree of accuracywherever it occurs. More particularly, the flash point will not bemissed in the early portion of the heating period due to an excessiverate of temperature increase, nor will it fail to be achieved in thelatter portion of the heating period due to a flattening out of thetemperature profile; the temperature continues to increase at about thesame rate until the ash point is reached.

Since the improved control system of this invention tailors the powerinput to the sample heater to meet the actual heat requirements of thesample being heated, there is never a wide temperature differentialbetween the sample and the heater. As a result, heat build-up on thesurface of the heater is avoided, thereby avoiding decomposition of theliquid sample and the resultant fouling that is often encountered inautomatic llash point testers. Moreover, all these advantages areattained with a completely automatic system, and with no chance ofoverheating due to the automatic limiting or safety features describedbelow.

For the purpose of indicating to the instrument operator when theinstrument is in the heating mode, a heating indicator lamp HL, mountedon the front panel of the instrument, is connected in parallel with theserially connected cartridge heater coil HC2 and transformer coil 35 sothat the lamp HL is energized and de-ener- .gized along with the coilHC2. That is, when the instrument is in the heating mode with thecartridge heater coil HC2 energized, the heating lamp HL is turned on,and when the instrument is in any other mode of operation, the heatinglamp HL is turned off.

To provide intermittent high voltage sparking between the two electrodes24, 25 within the flash chamber throughout each heating period (i.e., aslong as the cartridge heater coil HCZ, motor M1, and lamp HL areenergized), a series arrangement of a pulse generator 40 and the primarywinding T3a of the step-up transformer T3, is also connected in parallelwith the serially connected cartridge heater coil HCZ and thetransformer coil 35. Consequently, as long as the pole P6 of relay K3and pole P7 of relay TD1 remain in their normal positions, pulses fromthe generator 40 are transmitted through the transformer winding T3a,there-by generating corresponding stepped-up pulses in the secondarywinding T3b for application to the electrode pair 24, 25 to produce thedesired sparks. The sparking rate is thus accurately controlled `by therate of the output pulses from generator 40, which reliably generatespulses at a precise preselected frequency rate over long operatingperiods.

In order to provide a continuous record of the temperature of the liquidsample, and the flash points as they occur, the continuous temperaturerecorder 26 (FIG. 1) is operatively connected via terminals 41 and 42 tothermocouple TCL as shown in each of FIGS. 1 through 4. Thermocouple TCLSenses the temperature of the liquid sample in the passageway 14a (FIG.l) and will be referred to hereinafter as the liquid thermocouple. Asecond thermocouple TCV senses the temperature of the vapor in the flashchamber 16, and will be referred to as 'the' vapor thermocouple.

or llame ignited by the electrodes 24 and 25. Immediately upon theoccurrence of such a flash, therefore, the temperature of thevaporthermocouple TCV typically rises quickly about 200 F., applying an inputpulse to the winding LA1 of magnetic amplifier 33. This input pulsevturns the amplifier 33 on, producing an amplified output pulse whichautomatically initiates the following operations:

(l) Diversion of liquid sample `stream to air feed line for rapidcooling of flash chamber.

(2) Driving temperature recorder in a downscale direction. Y

(3) Reversal of the movement of the sliding contact on the variabletransformer.

(4) Termination of sample heating.

(5) Termination of sparking.

(6) Turning off heating indicator lamp and turning on cooling indicatorlamp.

(7) Initiation of a preselected timed cooling period, and

automatic termination of said cooling period and initiation of anotherheating period.

Returning to FIG. 4 for a more detailed description of the particularcircuitry fo-r carrying out the above functions, the output pulseproduced by the amplifier 33 in response to the triggering input fromthe vapor thermocouple TCV, energizes a mercury relay K2 to throw anormally open pole P3 to its closed position. The closing of the pole P3immediately energizes the fast-acting relay K3, thereby switchingassociated pole P6 from contact P6b to P6a to lock the relay K3 into thecircuit via pole P7. It will be recognized that pole P3 remains closedonly for the duration of the energizing pulse output from the amplifier33; to insure that the pulse width is Sullicient to hold the pole P3closed long enough to permit switching of the pole P6 to lock the relayK3 into the circuit, a capacitor 36 is connected across the coil ofrelay K2. This capacitor 36 serves to stretch the output pulse from theamplifier 33 to hold the pole P3 closed for the desired time.

In accordance with a further aspect of this invention, automatic controlmeans are operatively associated with the liquid and air feed lines andthe flash detection system for switching the continuous stream of liquidsample from the sample feed line to the air feed line in response to thedetection of a flash so as to effect rapid cooling of the ilash chamberbefore initiation of another test cycle. Thus, when the pole P6 isswitched to contact P6a, it energizes the solenoid 12a of the three-waysolenoid valve 12 (FIG. l) to turn the valve 90 clockwise from theposition shown in FIG. l, thereby diverting the continuous stream ofliquid sample from the normal feed line leading into the heating chamber13, to the air feed line 20 leading into the passageway 14a connectingthe heating chamber 13 and the flash chamber 16. The liquid entering thepassageway 14a through the air line 30 initially runs down into theheating chamber 13 until that chamber is lled, after which therelatively cool incoming liquidy passes upwardly through the passageway14a into the flash chamber 16. This provides rapid cooling of the ilashchamber 16 and the vapor thermocouple therein, with the cooling liquidbeing continuously drained out the bottom of the flash chamber via drainline 23.

As another aspect of this invention, automatic control means areoperatively associated with the continuous temperature recorder and theflash detection system to apply an overriding D-C signal to the recorderinput in response to the detection of a flash so as to drive therecorder pen downscale and prevent overshoot, thereby providing a clearand accurate indication of each detected llash. Thus, the energizationof relay K3 in response to a detected flash throwspole P5 to its closedposition, thereby applying a -negative D-C signal to the positiveterminal 41 of the recorder 26 and a corresponding positive D-C signalto the negative terminal 42to override the thermocouple signal and drivethe recorder pen downscale and prevent overshoot.- The overriding D-Csignal is obtained by converting the A-C signal from a transformer T2 toa D-C signal in a conventional A-C-to-D-C converter 43. Due to the fastaction of the relay K3, the overriding D-C signal -is applied to therecorder input immediately upon detection of a llash, so that theresulting temperature recorder has a clear and accurate indication ofeach flash point. The

lresulting temperature record is typically a saw-toothed curved with theupper peak of each tooth representing a. flash point.

During the cooling period, i.e., while the sample stream is being fedthrough the normal air feed line, the cartridge heater coil HC2, theheating mode motor M1, the heating lamp Hl., and the pulse generator 40(the active heating mode elements) are all turned off by the opencircuit at relay Contact P6b, due to the switching of pole P6. Duringthis same period, the circuit completed by the contact P6a and pole P6(l) energizes a cooling lamp CL, which is mounted on the frontinstrument panel to indicate that the instrument is operating in thecooling mode, and (2) reverses the movement of the sliding contact onthe coil 3S by energizing a cooling mode motor M2. The motor M2continues the reversed movement of the sliding contact throughout thecooling period, so the extent to which the contact is returned is, inelfect, a function of the length of the cooling period, since the motorspeed is normally fixed.

In order to time the cooling period, and automatically initiate anotherheating period at the end of the cooling period, the time delay relayTD1 is energized simultaneously with the energization of the relay K3.The time required for this relay TD1 to actuate the pole P7 associatedtherewith can 4be adjusted by a variable resistor R3 connected to therelay coil. A normal cooling cycle is about two minutes, but thevariable resistor R3 typically permits the cooling period to be setanywhere between 0.5 and 5 minutes.

At the end of the timed cooling period measured by the time delay relayTD1, the relay automatically throws the normally closed pole P7associated therewith to its open position. This immediately de-energizesthe relay K3 so that poles P5 and P6 return to their normal positionsshown in FIG. 4. As pole P6 returns from contact Pa to P6b, the circuitto the coil of relay TD1 is opened, thereby de-energizing the relay andreturning pole P7 to its normal closed position. At this point, thecircuit is once again in its original condition and, consequently,another test cycle is automatically initiated, beginning with a heatingperiod as described previously.

To briefly summarize the operations performed during one test cycle inthe illustrative instrument, at the start of each test cycle power issupplied to the electric heater to heat the continuous stream of liquidsampleV passing through the heating chamber. At the same time, theautomatic sparking device is actuated to produce repetitive sparkswithin the ash chamber, the heating light is turned on, the coolinglight is turned off, and the temperature recorder begins to record thesample temperature as indicated by the signal from the liquidthermocouple. These heating mode operations continue until a flashoccurs inside the flash chamber, with the power input to the electricheater being continuously increased by the motordriven variabletransformer. As soon as a flash occurs, the power supply to the electricheater is turned off, the variable transformer is automatically returnedto its starting position for the next cycle, and the liquid samplestream is diverted to the air feed line for cooling purposes. At thesame time, the automatic sparking device is turned off, the heatinglight is turned off, the cooling light is turned on, and the temperaturerecorder is driven downscale so that each peak on the resulting recordis an accurate indication of the detected llash point. These coolingmode operations continue for a preselected time period, after which theinstrument is automatically returned to the heating mode for anothertest cycle.

It will be appreciated at this point that in lined-out operation, themotor driven variable transformer 34 moves back and forth over a fairlyconstant range, but a sudden change in flash point level quickly resultsin a new range of travel either higher or lower than the previous range,depending upon the direction of the change in flash point level. If itis desired to shorten or lengthen the range of travel, this can beeffected by simply adjusting the timed cooling period by means of thevariable resistor K3. Thus, shortening the cooling period will shortenthe range of travel of the variable transformer and, conversely,lengthening the cooling period lengthens the range of travel.

In the illustrative system, the driving motors M1 and M2 for thevariable transformer are equipped with associated cams C1 and C2,respectively, which control the corresponding limit switches CS1 and CS2connected in series with the respective motors M1 and M2. During normaloperation of the instrument, the switches CS1 and CS2 remain in theirnormal closed positions illustrated in FIG. 4. However, if either motordrives the sliding contact on the `coil 35 beyond a preselected point,typically about 30% and 115% of input voltage, one of the cams C1 or C2immediately opens one of the switches CS1 or CS2 to de-energize theoperative motor. In other words, the cam-controlled switches provide amechanically responsive safety feature.

In keeping Iwith the present invention, a heat responsive safety meansis also provided, in the form of cartridge heater thermostat TS2connected in parallel with the pole P3 associated with relay K2. If thecasing 1 4 exceeds a preseleced temperature, typically 10 F. above therange of the instrument, the thermostat TS2 closes, thereby simulating adetected flash and initiating the same functions initiated by theclosing of the pole P3, as described above.

As can be seen from the foregoing detailed description, this inventionprovides an improved liash point testing device which automaticallydetermines the flash point of a liquid sample with a high degree ofaccuracy without the necessity of a preliminary estimate of the flashpoint to be determined. It has been found that the results obtained bythe completely automatic and continuous operation of this instrumentagree with results obtained by the Tag Closed Cup Flash Point testmethod (ASTM Test Method D-56) within plus or minus 2 F., and can bereadily correlated with Pensky-Martens Closed Cup Flash Point method(ASTM Test Method D-93). Moreover, the instrument of this invention iscapable of automatically detecting iiash points occurring over a widetemperature range without any preliminary setting for diiferentsarnples, and it greatly reduces the possibility of missing the ashpoint of any given sample, since the temperature is increased steadilyat a predetermined rate throughout the test. Consequently, the flashpoints are determined reliably in a single test, so that any given testdoes not have to be repeated, thereby reducing the overall testing timerequired for a large number of samples. Moreover, this instrumenteliminatesy or at least reduces decomposition of the liquid samplewithin the instrument, thereby eliminating the resultant fouling. Theinstrument requires little maintenance with attendant reductions ininstrument downtime, and increased efficiency. The switching of theliquid sample stream to the air feed line during the cooling periodprovides rapid cooling of the-instrument between successive heatingperiods, and the manual adjustment provided on the time delay relaypermits `different timed cooling periods to be selected for differentsamples or groups of samples, with automatic correlated adjustment inthe travel range of the motor-driven variable transformer which controlsthe heating rate. Finally, the automatically applied negative D-C signalwhich drives the temperature recorder downscale immediately upon theoccurrence of a ilash, prevents overshoots on the temperature record andprovides a clear and accurate record of the detected ash points.

We claim as our invention: y

1. An improved automatic flash point testing instrument comprising thecombination of means forming a flash chamber for receiving an air-vapormixture and including means for igniting said mixture, ash detectionmeans for detecting a flash in said flash chamber due to ignition ofsaid air-vapor mixture, means forming a heating chamber for heating aliquid sample to produce the vapor for said air-vapor mixture, a liquidsample feed line for supplying liquid sample to said heating chamber,

an air feed line for mixing air with the liquid sample between theheating chamber and the flash chamber, valve means interconnecting saidliquid sample feed line in said air feed line and automatic controlmeans operatively associated with said valve means and said llashdetection means for switching the stream of liquid sample from saidsample feed line to said air feed line in response to the detection of aflash so as to effect rapid cooling of the flash chamber prior toinitiation of the next test cycle.

2. An improved automatic flash point testing instrument as defined inclaim 1 in which said automatic control means includes asolenoid-operated valve operatively associated with said flash detectionmeans.

3. An improved automatic flash point testing instrument as defined inclaim 1 which includes heat responsive limiting means for simulating aash in response to a predetermined temperature of said liquid sample toterminate the heating of said liquid sample.

4. An improved automatic ash point testing instrument as defined inclaim 3 wherein said heating chamber includes electric heating means,and said heat responsive limiting means includes sensing means forsensing the temperature of the heated liquid sample, and control meansoperatively connected to said sensing means and responsive to apreselected sensed temperature for (l) cutting off the power input tosaid electrical heating means, (2) automatically switching the stream ofliquid sample from said sample feed line to said air feed line to effectrapid cooling of the flash chamber prior to initiation of the nexttestcycle, and (3) automatically turning on the power to said electricalheating means after a timed cooling period to start a new test cycle.

5. An improved ash point testing instrument as delined in claim 1 whichincludes first control means for carrying out a plurality of heatingmode functions and second control means for carrying out a plurality ofcooling mode functions, other than the switching of the liquid samplestream, a flash detection system including a differential thermocouplearrangement for detecting a flash in said flash chamber due to ignitionof said air-Vapor mixture and producing an output signal in response tothe detected flash, and a magnetic amplifier responsive to said outputsignal for producing a control signal to render simultaneously saidfirst control means inoperative and said second control means operative.

6. An improved flash point testing instrument as dened in claim 1 whichincludes a continuous temperature recorder including a thermocouple forsensing the increasing temperature of the sample leading up to adetected flash, said thermocouple generating an input signal for saidrecorder, and automatic control means operatively associated with saidrecorder and said flash detection means for applying an overriding D-Csignal to said recorder in response to the detection of a flashso as todrive the recorder downscale and prevent over'shoot, thereby providing aclear and accurate indication of each detected flash.

References Cited UNITED STATES PATENTS 2,634,360 4/ 1953 Kusa 219-5032,746,285 5/ 1956 Greanias 73--36 2,939,312 6/1960 Jacobs et al. 73-363,011,337 12/1961 MCGlynn 73-3'6 3,060,299 10/ 1962 Morgan 219-5033,368,388 2/1968 Christie et al. 73-36 3,402,595 9/ 1968 Kapff et al.73--36 RICHARD C. QUEISSER, Primary Examiner E. I. KOCH, AssistantExaminer

